1. Field of the Invention
This invention relates to quaternary ammonium group-containing organosilicon polymers and novel monomers used to produce these polymers. The invention also relates to methods of producing such polymers and monomers. The polymers may be used in wide applications as antimicrobial agents as, for example, in solutions to disinfect contact lenses and certain of these polymers may be used to produce solid structures, such as contact lenses.
2. Prior Art
Contact lenses are typically made of hydrophilic and partially hydrophilic plastic materials. These materials have a high capacity to absorb water and swell to a soft mass or hydrogel. This hydrogel is characterized by excellent mechanical properties, complete transparency, good shape retention and high resistance to degradation in boiling water. Such hydrophilic or partially hydrophilic plastic materials are described in such patents as U.S. Pat. Nos. 2,976,576, 3,499,862 and 3,503,942. These patents disclose, inter alia, the production of the so-called soft contact lenses.
One of the problems associated with cleaning soft contact lenses made from the aforementioned hydrophilic materials, is in the disinfecting and cleaning of such lenses. These lenses have a high capacity to absorb water, i.e. upwards of about 38 weight % water, based on the total weight of the hydrogel. Therefore, the compounds employed to disinfect the contact lenses are often absorbed and possibly even concentrated in the lenses and later released when the soft contact lenses are worn on the eye. This, of course, may damage or stain the contact lenses and harm the sensitive tissues of the eye. Such preservative or disinfectant materials typically used to disinfect the contact lenses may be such materials as chlorohexidine or thimerosal, for example.
To overcome these problems, materials such as quaternary ammonium group-containing polymers having antimicrobial activity may be used to disinfect the lenses. The advantage of using antimicrobial polymers is that they have a larger molecular size and are less likely to penetrate or be absorbed into the soft contact lenses, and tend to be less toxic.
Examples of such polymers are the polymeric quaternary ammonium compounds having recurring vinyl benzene ammonium units. Such polymers are disclosed in U.S. Pat. No. 4,482,680. These polymers have a disadvantage in that they have relatively poor solubility in water.
Another example of polymers employed for disinfecting contact lenses are the organosilicon quaternary ammonium compounds disclosed in U.S. Pat. No. 4,615,882. These polymers are produced by reacting an organosilicon quaternary ammonium salt having a hydrolyzable group with a water soluble high molecular weight organic polymer, such as polyvinyl alcohol, reactive with said hydrolyzable group. The hydrophilic polymers described in U.S. Pat. No. 4,615,882 have silicone and quaternary ammonium components as required in the present invention, however the synthesis of the polymers disclosed in the patent result in the formation of hydrolytically unstable linkages, e.g. silicon-oxygen-carbon linkages. The existence of such Si--O--C bond is unstable, breaks down over time, and could lead to toxicity problems.